Right now the scenarios I'll do three but I'll do them in general sense.
1) What if Naruto's and Sasuke's parents lived.
A lot of people seems to be obsessed over the concept that the overall theme of Naruto was, "Naruto was just suppose to be a nobody, he isn't suppose to be a child of destiny, he is just suppose to be a nobody." Not realizing the real point is, "Naruto was stripped of everything when he became the container for Kurama. He just became a weapon for the village, not really a person any more just a dangerous thing, the ultimate embodiment of the 'a ninja is not a person they are just a tool' philosophy that many ninja are taught from birth, and he had to struggle to get everything he should of had at birth." One of those being Sakura's affection.
Naruto would likely be told the story of how his parents got together when he was young. Which would give him the courage to compliment Sakura's forehead even when they were like 5 or 6. Sakura develops a crush on the Son of the Fourth Hokage that complimented her forehead, praises her, encourages her, and protects her from bullies. Kushina, if she learns of this, see Sakura as a little her. Then, makes it her mission to get those two together and get her some grandchildren. If you don't believe that would happen, you haven't been around any mothers with young kids. If a boy and girl are friendly at a park, if they are watching those two mothers will gush about how cute they look together, and dream about grandchildren they would give them. So, she takes Sakura under her wing. Sakura's parents support them getting together, as it gives Sakura the best possible future as Naruto will grow up to be the most eligible and desirable bachelor in the village.
Sasuke would be Naruto's best friend since birth. Their parents were best friends, and apparently Mikoto wanted to adopt Naruto once Kushina died. He would know that Naruto pretty much laid claim to Sakura very early on, likely played with both of them for years, also likely end up on a team with both of them, and the Sacred Rules inscribe upon every man's heart call The Guy Code would prevent him from really going after Sakura. And again, he would probably prefer to marry another Uchiha clan member like his father and brother did.
2) What if Sasuke didn't leave the village. What if Sasuke was informed of Orochimaru's intentions for his body and someone pointed out that without the plot and the world bending over backwards for him. He would have likely trick him. If not just out right imprison him and steal his body when he has the chance.
Well, Sasuke would remain in the village, since there is less of a reason to leave, but the 'what if' is always there in the back of his mind. That thought would come out whenever he hits a plateau or a roadblock in his training. Sakura might be glad that Sasuke hasn't left the village but the doubt, the fear, and what she saw in the Forest of Death will always stay with her. Naruto is told about the curse seal while his faith in Sasuke has never been shaken. He does nag Sasuke about the seal. Sakura becomes grateful to Naruto for helping return the team to some level of normalcy.
The problem is that Jiraiya still wants to train Naruto to get him ready for the Akatsuki return that may require Naruto to leave the village with him; to be on the road for a few years. This will make Sasuke jealous that he isn't being given this special training for his revenge. So, the adults Kakashi, Tsunade, and Jiraiya talk about what they should do. At first, they leave the team together to see how that works and if they don't. They eventually decided to do the individual focus training. Jiraiya for Naruto and Kakashi for Sasuke. The problem is Sakura, they note she would be a great if not perfect medical ninja. She however lacks the drive to endure the training Tsunade would give her. She got her drive originally from seeing how hurt Naruto gotten from trying to keep his promise to her and her swearing not to be a burden to him anymore. So, she either finds that drive or languish in mediocrity. Story-wise she has to get that drive and it preferably has to come from one of her two teammates. Now be honest everyone, do you think Naruto is going to give her that drive/encouragement or Sasuke?
Then comes Karin who joins the village to be with Sasuke. If she is allowed and they discover she is an Uzumaki, Naruto gets a cousin. Naruto would probably want to get to know and bond with his only family. He also may be willing to help his only family member get with the boy she is in love with, who is also his best friend. So, with Naruto help and being Sasuke's type, she makes both incredibly and relatively quick gains to becoming the one in the lead to being with Sasuke. Sakura with start to doubt herself and Sasuke's feelings for her when another girl just appeared and was able to surpass her that fast.
Naruto is not bound by the Promise of a Lifetime, so he is free to pursue Sakura. Karin would probably help him in return for helping with Sasuke. Sasuke might just make it clear to Sakura he isn't interested in her and tell where what really happened.
Also, as I said before the time they were together as Team 7 before the chunin wasn't that long. Anywhere from maybe 3-6 months. While the time from when Sasuke left the village to the ending is about 3-4 years. That means at a minimum they would spend six times to as much as sixteen times together with the issues and lack of trust driving their bond into the dirt. Or more likely Sasuke getting sick of her pining after him and making it clear he doesn't like her.
So Part 2 would be NS and SK already set, if not together, as the final pairing just them developing further into that.
3) What if Sasuke returned before Kishimoto had a mandate to put nH/SS together. That is everything between what if he was dragged back at the end of part one, to he comes back willing during some part in the middle of part two, and even what if Kishi had continued the story past the war arc so didn't get the mandate to set up the sequel.
Naruto uses every last ounce of influence he has in the village to get Sasuke a pardon for his crimes. Afterwards for a few weeks he decides to give Sasuke and Sakura some distance before trying to win Sakura again; a reset of the relationships. Everyone, well mostly everyone, knows what he is doing. Sasuke isn't into Sakura and doesn't want to be with her unless he feels the need to atone for how he treated her. While Sakura is upset at Naruto keeping his distance from her.
Sai eventually has enough and confronts Sasuke to help out his friends. The two of them have a spat about how they are his friends not his. Then Sasuke goes to Sakura and ends any possibility of them getting together and pushes her towards Naruto.
Sakura confronts Naruto asks him why he did it. He confesses his feelings. They end up together.